1) Field of the Invention
The present invention relates to the improvement of a sequential segment joining stator coil type electric rotating machine (rotary electric machine), and more particularly to the improvement of a vehicle-mounted electric rotating machine of the same type.
2) Description of the Related Art
In the case of an idle stop system which is gradually in employment in the recent years, there is a requirement for starting an engine frequently, and this calls for a brushless type AC motor in place of a brush-needed DC stator. However, a large-starting-current AC motor standing comparison with a conventional DC series starter falls into an increase in size, which requires the enlargement of a space of the engine room or a considerable alteration of the layout therein. One countermeasure against this problem is the division of a stator coil, i.e., the employment of a radial series coil construction.
Meanwhile, as an AC generator for use in vehicles, there has been employed a sequential segment joining stator coil type electric rotating machine which was developed by the Applicant of the present application. This electric rotating machine can provide a simple conductor arranging construction at a coil end portion and can enhance the slot space factor and, hence, achieves size/weight reduction and superior heat radiation of a stator coil, and it is suitable for use as an idle stop AC motor which temporarily requires the supply of a large starting current. However, taking into consideration the employment as a running motor for use in hybrid vehicles, fuel cell powered vehicles or secondary battery powered vehicles, a considerably larger current supply thereto becomes necessary, as compared with a vehicle AD generator with the aforesaid sequential segment joining stator coil.
For the supply of a large current to an electric rotating machine, there have been known various manners including the enlargement of a segment cross section and the division of a stator coil. However, the actual implementation of these manners encounters difficulty on manufacturing. In the meantime, for the enhancement of the output of a vehicle-mounted electric rotating machine and the reduction of the wiring loss, there is also a requirement to handle a high voltage, i.e., for an increase in number of turns. However, in the case of the sequential segment joining stator coil, because of a low degree of freedom on the wiring alteration, difficulty is experienced in accomplishing the employment of a radial series coil construction and the increase in number of turns at the same time. In particular, the simultaneous approach to the increase in number of turns and the increase in number of radial series coils creates various problems, such as complicating the wiring connection construction at a coil end portion.
That is, in the case of a conventional sequential segment joining stator coil, difficulty is encountered in supplying a large current through the use of a parallel circuit arrangement due to a limitation on the segment arrangement pattern and difficulty is experienced in handling a high voltage due to a limitation on the increase in number of turns.
The present invention has been developed with a view to eliminating these problems, and it is therefore an object of the present invention to provide a sequential segment joining coil with a large-current-supply permitting multi-turn construction, capable of easing the complication of the inter-segment connection pattern and of reducing the variation in electromotive voltage between parallel circuits.
For this purpose, in accordance with a first aspect of the present invention, there is provided a sequential segment joining stator coil type electric rotating machine comprising a rotor having p pairs of poles (where p represents a natural number equal to or more than 2), a stator core including a large number of slots each having s conductor accommodation positions (where s represents an even number equal to or more than 6) in its radial directions, and an armature winding including m-phase windings (where m represents an odd number equal to or more than 3) made by sequentially connecting a large number of U-shaped segments, with each of the U-shaped segments being composed of a U-shaped head portion made to constitute a head-side coil end, a pair of in-slot conductor portions to be respectively accommodated in a pair of slots separated by a predetermined slot pitch from each other and a pair of protruding end portions made to protrude from the slots to constitute an end-side coil end and tip portions of the pair of protruding end portions being respectively joined to tip portions of other protruding end portions adjacent thereto in a radial direction, wherein in-phase slot groups are provided for each pole, each including a plurality of in-phase slots signifying the slots accommodating the in-slot conductor portions constituting the phase windings in phase with each other and continuously arranged in circumferential directions for each pole, and the conductor accommodation positions of the slots are divided into r (where r=s/t) conductor accommodation position sets each composed of t (where t represents an integer) conductor accommodation positions continuously located in radial directions, and the in-phase slots identical in order of position from one of circumferential directions of the in-phase slot group accommodate a partial coil in each of the conductor accommodation position sets, and the phase winding is constructed in a manner such that radial series coils formed by connecting the partial coils of the conductor accommodation position sets different from each other in series to each other through an inter-layer connection line, which are equal in number to the in-phase slots of the in-phase slot group, are connected in parallel with each other.
That is, according to this aspect of the present invention, the partial coils pertaining to the conductor accommodation position sets different from each other in radial directions are connected one by one in series to each other to form the radial series coils which are equal in number to the in-phase slots of the in-phase slot group, with these radial series being connected in parallel with each other.
Thus, the partial coils accommodated in the conductor accommodation position set comprising a plurality of conductor accommodation positions existing continuously in radial directions of the in-phase slots taking the predetermined order of radial position in the in-phase slot group can be connected in series and in parallel to each other without complicating the connections between the partial coils. Accordingly, by increasing the number of partial coils in circumferential directions or in radial directions, it becomes possible to easily realize the supply of a large current to the sequential segment joining stator coil and the handling of a high voltage therein. In consequence, this realizes a sequential segment joining stator coil which is capable of coping with a high voltage and a large current, which has been considered so as not to be easy so far.
A further explanation will be given below. The conventional sequential segment joining stator coil creates a problem in that difficulty is experienced in carrying a large current through a parallel circuit arrangement due to a limitation on the segment location pattern and difficulty is experienced in handling a high voltage due to a limitation on the increase in number of turns. On the other hand, a large number of partial coils composed of simple sequential segment joining coils are sequentially connected in circumferential directions and in radial directions to complete a phase winding forming a partial-coil series/parallel-connected circuit, thereby simplifying the arrangement of connection lines among the partial coils and easily avoiding the mutual interference among the connection lines. This can not only reduce the occupying space of the connection lines to be located at the head-side coil end, but also reduce the size and weight of the electric rotating machine accordingly, and even reduce the resistance loss and heat generation in the connection lines.
Therefore, in particular, the sequential segment stator coil type electric rotating machine according to the present invention is effective in a case in which a conventional 14-V battery for a vehicle is voltage-boosted (for example, up to 42V). Meanwhile, for example, if the connection state of three partial coils organizing a radial series coil of a phase winding is changed from the series connection to the parallel connection, it can also function as a conventional 14-V vehicle electric rotating machine.
Preferably, the series connection between the partial coils organizing a radial series coil is realizable through the use of a dedicated connection segment. In this connection segment, a pair of in-slot conductor portions can also function as head in-slot conductor portions of two partial coils adjacent to each other in a radial direction (it is also acceptable that they are shifted in a circumferential direction) and the last in-slot conductor portions.
In a preferable mode, the combinations of the partial coils constituting the radial series coils of the phase winding are determined so that the total theoretical vector electromotive voltages (electromotive forces) of the respective radial series coils become equal to each other.
There is a problem which arises with the above-described partial-coil series/parallel connection type sequential segment joining stator coil in that, since the partial coils constituting each of the radial series coils are shifted in a circumferential direction, a phase difference occurs between the theoretical vector electromotive forces of the partial coils, which makes a difference in the total theoretical vector electromotive force (voltage) between the radial series coils. This difference between the theoretical vector electromotive forces develops a circulating current circulating through two radial series coils constituting a phase winding, which causes the heat generation of the electric rotating machine, the loss, the enhancement of noise, and the lowering of the efficiency and output.
For this reason, in this mode, the combinations of partial coils constituting radial series coils are selectively set so that the vector sums of the theoretical vector electromotive forces of the partial coils of the radial series coils become equal to each other, in other words, so that the vector sum of the theoretical vector electromotive forces in each of the radial series coils agrees with the vector sum of the theoretical vector electromotive forces in the other radial series coil. This prevents the circulating current from circulating through the radial series coils, that is, solves the above-mentioned problem.
In a preferable mode, of the inter-layer connection lines of the respective radial series coils, the inter-layer connection lines located at the same position in a radial direction are separately placed in the in-phase slot groups different from each other in a circumferential direction.
That is, a partial coil is constructed in a manner such that the in-slot conductor portions accommodated in specific in-phase slots existing at an interval of one pole pitch in a circumferential direction are connected in series to each other in the same conductor accommodation position set. At this time, in the case of the same current supplying direction, even if, of these in-slot conductor portions, the in-slot conductor portion at any position in the circumferential direction is used as a head in-slot conductor portion of this partial coil, the electromagnetic equivalence is attainable.
Therefore, in this mode, in order to prevent the inter-layer connection lines of the radial series coils from overlapping spatially with each other, the inter-layer connection lines existing at the same position in circumferential directions of the radial series coils are shifted in the circumferential directions. In this connection, it is preferable that the inter-layer connection lines existing at the same position in radial directions are shifted by one pole pitch for the purpose of shortening the wiring distance of radial crossover which takes place afterwards. This can shorten the axial length of the inter-layer connection line occupying space and the overall length of the inter-layer connection lines, thus further promoting the above-mentioned effects of the present invention.
In a preferable mode, the partial coil is constructed in a manner such that wave winding segments forming segments passing through the first and fourth layers of the conductor accommodation position set in its radial directions and lap winding segments forming segments passing through the second and third layers thereof are alternately connected to form first and second circling coils which substantially make a circuit, and shape-different wave winding segments forming the last in-slot conductor portion of the first circling coil and the head in-slot conductor portion of the second circling coil are connected in series thereto, with it being accommodated in one in-phase slot of the in-phase slot group which has a predetermined order in a circumferential direction.
Thus, the radial connection segments forming the inter-layer connection lines can easily be placed while avoiding the spatial interference with the lap winding segments or the wave winding segments. Moreover, multi-turn partial coils can be constructed while avoiding the complication of the coil end construction, and since a pair of in-slot conductor portions of a radial connection segment forming an inter-layer connection line constitute a head or last in-slot conductor portion of each of the partial coils, the connection operations among the partial coils can continuously be conducted in the other segment joining process and the simplification of the process is achievable.